Devices for treatment of orthodontic overbite have been proposed. In the early 1900's, German orthodontic practitioners were well aware of the efficacy of incline planes to resolve overjets (overbite). As approximation of the teeth occurred, the inclined plane attached to the mandible contacted the inclined plane of the maxilla. As closure progressed, the lower jaw was forced into a protruded position as dictated by the inclines. Since correction of the overjet depended on constant protrusion of the mandible to effect cellular changes required to eventually result in the new and desired lower jaw position, it was necessary that patients so treated hold the teeth in constant contact. Holding teeth in the contact position required constriction of the muscles which protrude the lower jaw (pterygoids), whereas relaxation of those muscles resulted in the teeth losing contact and the lower jaw being allowed to retreat to its former position. With the jaw in its former position, no orthopedic cellular change and hence no permanent overjet correction would be realized.
Emil Herbst, in his early 1900 work "Zahnarztliche Orthopadie" stated:
"When many unsuccessful results through the use of inclined planes occurred, the reason was that many patients avoided the "stressed" position. Instead of holding their teeth closed or in contact with the inclined plane and allowing (or forcing) the muscles to function, it was more comfortable to hold the mouth open and avoid the strain . . . , that an incline plane can only be effective, when the teeth are truly in contact, and that on the other hand, many patients, especially uncooperative, lazy or unmotivated children, relax muscle pressure by holding the mouth open, I constructed a guide that would work against this relaxation (from holding the mouth open)."
It is reasonable to conclude that if an inclined plane in one direction eliminates an overjet, an inclined plane in the opposite direction may create or exacerbate an overjet. By "adverse inclined plane" what is meant is an inclined plane in the reverse direction. In the mouth there is a naturally occurring adverse inclined plane. That inclined plane is the relationship of the lower incisor tips in contact with the lingual surfaces of the upper incisors. FIG. 1 shows how increasing overbite results in increasing overjet or, as in the case of a mandible which has been forward-postured by an inclined plane-type of appliance, how the excess overbite and the contact between the lower incisor tips and the lingual surfaces of the upper incisors, results in retrusion of the mandible forcing it back into its original position thereby reversing those orthopedic changes previously derived.
Additionally overbite orthopedic correction appliances which have been employed have been subject to failure. Appliances for providing Herbst therapy are described in Mason, U.S. Pat. No. 4,551,095, Jones, U.S. Pat. No. 4,462,800 and Kumar, U.S. Pat. No. 5,183,338. The two common sources of failure are metal fatigue and inadequate weld or solderjoints. All oral appliances are subject to the harsh dynamics associated with chewing, speech, and swallowing. During, for example, swallowing, there is motion associated with the lower jaw while the upper and lower jaws are closed together. Humans swallow in excess of 1000 times a day just to lubricate the pharyngeal mucosa. As a result of these oral dynamics, the metal parts of the appliance are stressed and flexed leading to metal fatigue and failure.
It is logical to conclude that by harmonizing the sizes of the components of an appliance, failure as a result of fatigue can be reduced. Further by eliminating or reducing welds, the incidents of failure can be reduced.